PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.New Womens Roxy Mocha Shoes Style 114199 Brown 418CD dr , Black Patent Leather AK ANNE KLEIN Low Back Slides 6.5 MWomen's Mephisto Cool Air Brown Patent Leather Mules Flats US 6Okabashi brown closed toe Mule / Slides OKA B Womens US size mediumMERRELL Lotus Roast Women's Size 7.5 Brown Leather Slip-on Wedge Comfort ShoesDuck Head 7.5 M Women Mules Clogs Brown Woven Wedge Heel Leather ComfortMerrell 8.5 M Encore EMME Black Suede Fabric Flats Mary Janes Casual , UJoowalk Womens All Black Comfortable Casual Canvas Slip On Fashion Sneakers ...Munro American "Josie" Red Leather Ballet Flats. SZ 7.5 M NEW DISPLAY--- D2841Frye Gemma Slip Tassel Ash Women's 7 - 7 1/2 MISMATCHEDROCKET DOG Shoes 6.5 Ballet Flats Red Velvet Wedge Slip Slide On Womens NewBCBG Max Azria Black Rubber Brooch Ballet Flats Size 6 , Stuart Weitzman Crocshoestring Black Sioux Croco Ballet Flat Size 6.5M E204Vince Camuto Safari Leather Brindy Fashion Sneakers Women’s Shoes Size 6MMephisto Leather mules shoes loafers made in Portugal size 8.5 , Spring Step Ferrara Slip On - Women's Size 8.5M GrayNRS Kicker Remix Women's Blue/Black Wetshoe 6MAdidas Ecstasy Mid Sleek Series Hi White Multi Trainers G51414 Size 7.5 US 6 UK , JOY & MARIO Womens El Porto California Stripes Slip-on Espadrille Flat Shoes Red , Women's SanWomens Spadrille- Pick SZ/Color. Strong Resistance To Heat And Hard Wearing Flats , Women's Jelly Pop Size 3 Boots Ideal Gift For All Occasions Flats , [365830-04] New Women's PUMA Platform Trace Sneakers - Aqua Blue WhiteSkechers BOBS Women's Beach Bingo-Dapper Party Sneaker - Choose SZ/ColorAmerican Yorkshire Pig Print Christmas Running Shoes For Women- Free Shipping , Womens Air Huarache Run Print Black Haki-White 725076-007 Leopard Khaki New Walk , PUMA Womens Vikky Platform- Select SZ/Color.Adidas Women's Superstar Slip-On Originals Casual ShoeSkechers Women's Empress - Solo Mood Casual Shoe , WMNS NIKE BLAZER MID '09 ND 375573-661BEET/VIOLET SIZE AVAL.8~12 WAS $85.00Softwalk Simba Slip On Lightweight Comfort Loafer Black Womens Size 8
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."